Ferrite loaded wave-guide adapted for progressive magnetic saturation



Sept. 21, 1965 M. STIMLER FERRITE LOADED WAVE-GUIDE ADAPTED FOR PROGRESSIVE MAGNETIC SATURATION Filed NOV. 2. 1961 FIC.1.

INVENTOR. MORTON STIMLER United States. Patent 3,208,014 FERRITE LOADED WAVE-GUIDE ADAPTED FOR PROGRESSIVE MAGNETIC SATURATION Morton Stimler, Hyattsville, Md., assignor to the United States of America as represented by the Secretary of the Navy Filed Nov. 2, 1961, Ser. No. 149,787 4 Claims. (Cl. 33324) (Granted under Title 35, US. Code (1952), see. 266) The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

This invention relates to a ferrite material for wave guides and coaxial lines and more particularly to a ferrite core having a taper to provide for progressive saturation thereof.

In this invention, the principle of controlled progressive saturation is applied to ferromagnetic materials such as ferrites. A magnetic material having a tapered surface such as a solid cone or a pyramid may have a progressive saturation boundary induced in it. This is a phenomenon which is produced when a magnetic field is applied to such a core of ferromagnetic material in which the number of lines of magnetic flux required to saturate a portion of smaller volume having a smaller cross sectional area.will be less than the magnetic flux required to saturate a portion of larger volume having a larger cross sectional area. If a gradually increasing magnetic field is applied to the tapered ferrite core, the portions of smaller cross section will become saturated first and the portions of larger cross section will become progressively saturated as the strength of the magnetic field is increased. By applying an increasing voltage such as that from a sawtooth or alternating current generator, for example, to a coil surrounding a tapered ferrite, the ferrite will be saturated in a progressive manner, that is the portions of small cross sectional area first when the voltage is small and then portions of increasingly greater cross sectional area will be saturated if the current increases sufficiently during each cycle of operation. Many uses for ferrites in electromagnetic wave guides may be found in an article entitled Behavior and Applications of Ferrites in the Microwave Region by A. G. Fox, S. E. Miller, and M. T. Weiss in the Bell System Technical Journal, January 1955, vol. 34, pp. 5- 103.

An object of this invention is to provide a tapered ferrite sleeve or core within a coaxial cable.

Another object of this invention is to provide a tapered ferrite core within a wave guide.

A further object is to provide a tapered ferrite member within an electromagnetic wave guide element and means for partially saturating the ferrite member whereby a reflection of the electromagnetic wave is effected at the saturation boundary.

Another object of this invention is to provide a system for progressively reflecting electromagnetic waves wit-bin a wave guide including a tapered ferrite core disposed within the wave guide and a coil surrounding the wave guide for providing a progressively increasing magnetic field in said ferrite.

A still further object is to provide a tapered ferrite core within a coaxial cable and a sweep voltage applied to the inner conductor to provide an increasing magnetic field whereby the ferrite may be progressively saturated.

Other objects and many of the attendant advantages of this invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawing in which like reference numerals designate like parts throughout the figures thereof and wherein:

FIG. 1 illustrates an embodiment of this invention in which a ferrite core is mounted within a coaxial air line;

FIG. 2 illustrates an embodiment of this invention in which a tapered ferrite core is mounted within a wave guide; and

FIG. 3 illustrates a circuit suitable for use with the ferrite section of this invention.

Referring now to FIG. 1 of the drawing in which a tapered ferrite section in a coaxial line is illustrated as a typical embodiment of this invention, an inner conductor 11 and an outer conductor 13 with end connectors 15 and 17 form a coaxial line section within which a tapered conical ferrite core 19 is disposed.

The space between the ferrite core and the inner surface 21 of the outer conductor may be filled with a nonmagnetic dielectric either gaseous or solid, as desired.

Referring now to FIG. 2 of the drawing in which a second embodiment of the invention is illustrated, a ferrite core 23 is shown mounted within a rectangular wave guide 25. A dielectric non-magnetic material 27 is shown filling the space between the tapered portion of the ferrite core and the inner walls of the wave guide. This material may have the same dielectric constant as ferrite 23 when the ferrite is saturated. The ferrite core 23 may be tapered on two sides with the remaining two sides being parallel or it may be tapered, if desired, on all four sides for rectangular wave guides or, if desired, the ferrite core 23 may be conical for circular wave guides. A coil 29 with a D.-C. energizing source 31 and a voltage varying means 33 is shown with the coil surrounding wave guide 25. The coil 29 and voltage source 31 are employed to provide an axial magnetic field through ferrite 23. A periodically varying voltage source such as a sawtooth or alternating current generator may be used in place of voltage source 31 and voltage varying means 33, if desired.

Referring now to FIG. 3 of the drawing in which a circuit diagram for the ferrite core installation is illustrated, a length of coaxial line is shown having an inner conductor 51 and an outer conductor 53. A tapered fer rite core 55 is disposed within the outer conductor of the coaxial line. The coaxial line is fed by a high frequency voltage source 57 connected to inner conductor 51 and outer conductor 53. A line termination impedance Z terminating the coaxial line may have the same impedance as the characteristic impedance of the line such that all of the high frequency signals which pass through the ferrite core are absorbed thereby rather than reflected.

A source of variable unidirectional current 59 such as, for example, a sawtooth generator is shown connected through coaxial Ts 61 and 63 to the inner conductor 51 of the coaxial line, and the current source 59 may provide voltage variations other than the sawtooth illustrated.

The operation of the circuit of this invention may now be considered with reference to FIGS. 1 and 2 of the drawing. In FIG. 1, the tapered ferrite core 19 may be considered as comprised of radially parallel sections cut by planes perpendicular to the axis of the core, each section of which has a slightly greater cross sectional area than the preceding section. The sections having the smallest cross sectional area will saturate first as the sawtooth voltage is first applied and then sections of larger area will become saturated as the magnitude of the sawtooth voltage becomes greater as the number of lines of magnetic force increase with such increase in voltage.

Obviously many modifications and variations of the present invention are possible in the light of the above teachings. It is therefore to be understood, that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described.

What is claimed is:

1. In a coaxial line having an inner conductor and an outer conductor having an inner diameter, a solid conically shaped ferrite core disposed within said line and concentric therewith, the base of said ferrite core having a diameter equal to the inner diameter of said outer conductor, and means connecting said inner conductor to a source of unidirectional voltage pulses, each of said pulses having an increasing potential with respect to time, whereby said ferrite may be progressively magnetically saturated by each of said pulses.

2. A coaxial line having an inner conductor and an outer conductor, said outer conductor having an inner cylindrical surface, a conically shaped ferrite core concentrically disposed within said outer conductor, said ferrite core having a base and a tapered surface, said base having a diameter equal to the diameter of the inner surface of said outer conductor, dielectric means filling the space between the tapered surface of said ferrite core, and the inner surface of said outer conductor, said inner conductor being energized in a manner to apply an increasing magnetic field with respect to time about said ferrite core whereby said core may be progressively saturated.

3. In a wave guide system for conducting high frequency radiant energy, a wave guide, said wave guide having internal wall surfaces, a ferrite member having a base and an apex portion with tapered surfaces therebetween, said ferrite member being disposed centrally within said wave guide such that said base fills the space between said inner wall surfaces, a dielectric disposed within said wave guide such as to fill spaces between the tapered surfaces of said ferrite member from said base to said apex portion, means for applying a magnetic field to said ferrite member, said magnetic field having an intensity which varies as a function of time such that said ferrite member may be progressively saturated.

4. A coaxial transmission line for conducting high frequency radiant energy comprising an inner conductor, a hollow cylindrical outer conductor, said outer conductor having an inner cylindrical surface, a ferrite core disposed concentrically within said outer conductor, said ferrite core having a base and an apex with a tapered surface therebetween, said base having the same diameter as the inner surface of said outer conductor, a dielectric disposed between said ferrite core and the inner surface of said outer conductor, means applying an increasing current in said inner conductor whereby said core may be progressively saturated.

References Cited by the Examiner UNITED STATES PATENTS 2,894,209 7/59 Chodorow et al. 332--29 2,894,224 7/59 Iversen 333-34 3,078,425 2/63 Duncan 333-24 FOREIGN PATENTS 1,065,039 9/59 Germany.

OTHER REFERENCES Burgess: Ferrite-tunable filter for use in S band. Proceedings of the I.R.E., vol. 44, No. 10, page 1461.

HERMAN KARL SAALBACH, Primary Examiner.

ELI LIEBERMAN, Examiner. 

1. IN A COAXIAL LINE HAVING AN INNER CONDUCTOR AND AN OUTER CONDUCTOR HAVING AN INNER DIAMETER, A SOLID CONICALLY SHAPED FERRITE CORE DISPOSED WITHIN SAID LINE AND CONCENTRIC THEREWITH, THE BASE OF SAID FERRITE CORE HAVING A DIAMETER EQUAL TO THE INNER DIAMETER OF SAID OUTER CONDUCTOR, AND MEANS CONNECTING SAID INNER CONDUCTOR TO A SOURCE OF UNIDIRECTIONAL VOLTAGE PULSES, EACH OF SAID PULSES HAVING AN INCREASING POTENTIAL WITH RESPECT TO TIME, WHEREBY SAID FERRITE MAY BE PROGRESSIVELY MAGNETICALLY SATURATED BY EACH OF SAID PULSES. 